The present invention relates to machine tools, and more particularly to a jig grinder having automated reciprocation and outfeed control.
Jig grinders are used by machinists to accurately grind precision holes, radii, blends, and surfaces in metal or other materials. These machine tools are used in the manufacture of a wide variety of high precision products. For example, jig grinders are used by the automotive and aerospace industries for producing engine parts, gears, and the like. Although extreme precision is the primary goal of such application, productivity is a main concern, particularly in keeping the cost of individual machine parts as reasonable as possible. Accordingly, recent advances in jig grinder design have concentrated on automatiing the grinding process in an effort to increase machine through-put while maintaining accuracy.
Various grinding techniques which can be accomplished with jig grinders are well known. One such technique is the use of "chop grinding" in the generation of contours. The chop grinding principle utilizes a rapid reciprocation of the grinding wheel in a direction along the wheel axis. It has been found that this technique grinds cool, providing more consistent surface finishes, geometry and size than other, more conventional grinding techniques.
Chop grinding can be used to machine holes and edges as well as radii. There are several different motions which occur simultaneously during a chop grinding process. One motion is that of the grinding wheel which rotates, typically at a high rate of speed. The grinding wheel can also be rotated in a planetary manner with respect to the jig grinder spindle, for example when chop grinding a hole. As noted above, the grinding wheel will also be reciprocated up and down, along the axis thereof. Reciprocation of the grinding wheel occurs along the "Z'-axis" of the jig grinder. Finally, as the grinding of a surface progresses, the grinding wheel will be indexed toward the surface being ground until the desired amount of stock has been removed from the work being machined. This latter movement is referred to as "outfeed". For purposes of the present specification, the outfeed movement is referred to as movement along the "U-axis" of the jig grinder.
In the past, jig grinders have been largely manually operated. In performing a chop grinding task, a machine operator would manually index the grinding wheel against the surface to be ground, and commence grinding with a rotating and reciprocating grinding wheel. As material was ground away from the surface of the workpiece, the machine operator would manually outfeed the grinding wheel until the required amount of material was ground off. Upon each outfeed operation, the grinding wheel would create a shower of sparks as it proceeded to strip material from the grinding surface. A machine operator would then wait until the sparks stopped, indicating that the grinding wheel had removed all of the stock up to the outfed position (or the grinding wheel had worn to a point where an outfeed adjustment was necessary). The operator would then manually repeat the cycle until the finished dimensions were reached.
Wipe grinding, which is a technique wherein the grinding wheel is not reciprocated, has also been done manually in the past. An operator would bring the grinding wheel to the surface to be ground, and manually index the grinding wheel toward the workpiece until the required amount of stock material had been removed. When wipe grinding, an operator would slowly and repetitively feed the grinding wheel toward the surface being ground.
It would be advantageous to provide a jig grinder which is automated to reduce the number of manual operations required of the machine operator. Such an automated machine tool would increase machine productivity and preserve, if not improve, the accuracy to which parts are machined. The present invention relates to an automated machine tool in which these and other advantages are achieved.